Whispering gallery mode pressure sensing

Optical resonances of microresonators, also known as whispering gallery modes, are attracting considerable interest as highly sensitive measuring devices with a variety of applications. Such resonators can be used for pressure, force or strain measurement. Droplets, embedded in an appropriate substrate, form perfect spheres due to their surface tension and can be used as optical resonators with high quality factors. The resonance frequencies of these droplets depend sensitively on their size and shape. Pressure changes affect the droplet shape. Therefore, pressure change can be measured with high sensitivity. In the work presented here, ethanol droplets embedded in a silicone matrix are considered. The shift of the resonance frequencies of microdroplets embedded in silicone as function of the applied pressure is investigated.